TubeNet

I am going to be traveling to London and Glasgow in the next 2 months and I was wondering if there are any good places to try tubas. I'm going into university next year and will eventually need a high horn. I currently play in a british style brass band (among about 6 other groups) but I'm doing it on my C and I would really like to try a Besson 983. I'd also like to try anything else that is avalible to play. Any help would be greatly appreciated.